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2011-04-12 12:11:20
ASBOG Exam Chemical Rocks

ASBOG Study guide - Chemical Rocks
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  1. Limestone: Chem formula, formation, location
    Calcium Carbonate. CaCO3 . Formed either by accumulations of limy sand and muds from chemical precipitation or may form from calcium carbonate-secreting organisms.

    Warm, shallow tropical waters that are slightly supersaturated with respect to calcium carbonate
  2. Dolomite: Chem formula, formation, location
    (CaMg(CO3))2 . Precipitated directly from waters in higly saline tidal flats. Pore space enriched in Mg ions due to evaporation
  3. Diatomite: Formula, formation, location
    Formed from the consolidation of diatomaceaous oozes (silica oozes from diatoms, radiolarians or sponges)
  4. Chert: Formation, location
    Amorphous or extremely fine grained siclia found in concretions and beds. Orginates in costal waters. Believed to be formed by silica-secreting organisms
  5. Pyrite: Formula, formation
    FeS2 . Fromed by the indirect action of bacteria. Bacteria change sulfur from an oxidized state (sulfate - SO4-2) to a reduced state (sulfide - S-2). Hydorgen sulfide is produced, which changes Ferric iron (Fe+3) to Ferrous iron (Fe+2)
  6. Peat to Coal: Formation
    Peat is formed when decaying vegetation does not have enough oxygen. After burial and chemical transformation peat becomes lignite. More time, deeper burial and higher temp lignite -> bituminous -> anthracite coal
  7. Evaporates: Formation, mineral sequence
    Formed by the evaporation of sea water. Calcium carbonate (Calcite) -> calcium sulfate (Gypsum or anhydrite) -> Sodium chloride (Halite) -> magnesium sulfates and chlorates -> sodium bromide and potassium chlorides